The invention relates to a former for a web producing machine. The former of the invention is of the kind having a pressure shoe that presents a sliding surface which, viewed in a section taken in the running direction of the web, is curved convexly. An endless wire belt or screen, called a wire, is guided by the sliding surface of the pressure shoe.
Numerous formers of this kind are known. One example is described in German Laid-Open Patent Specification (DT-OS) No. 2,248,454 and corresponding U.S. Pat. No. 3,832,282. See, in particular, FIG. 1. This former has two wires which together form a wedgeshaped entry slot for the pulp suspension and the wires are then jointly conducted, with the paper web which is being formed, over the pressure shoe. The pressure shoe may be constructed as a suction box.
Although it has numerous advantages, this kind of double wire web producing machine also has disadvantages. There are added expenses involved in using a second wire as such. Extra problems arise in controlling the running of the wires.